creating that signature. Section 5.5 of [DKIM] lists
RFC5322.Subject as one that should be covered as it contains
important user-visible text, so this is expected to be an issue
for any list that makes such changes.

It should say:

creating that signature. Section 5.4.1 of [DKIM] lists
RFC5322.Subject as one that should be covered as it contains
important user-visible text, so this is expected to be an issue
for any list that makes such changes.

Notes:

----- Verifier notes -----
The section reference was correct when the DKIM reference was RFC 4871, but as 6376 and 6377 were published together, the reference was not changed accordingly. Oops.